Rotating flame spreader for stationary flameholder



Dec. 1, 1959 w. D. PoucHoT ROTATING FLAME SPREADER FOR STATIONARYFLAMEHOLDER Filed fla 15, 1957 2 Sheets-Sheet l INVENTOR WALTER D.POUCHOT ATTORNEY I Dec. 1, 1959 w. D. PoucHoT 2,9

ROTATING FLAME SPREADER FOR STATIONARY FLAMEHOLDER Filed May 15, 1957 2Sheets-Sheet 2 22!) F 19L2 4 F X 2n INVENTOR WALTER D. POUCHOT MW RMATTORNEY ROTATING FLAME SPREADER FOR'STATIONARY FLAMEHOLDER ApplicationMay 13, 1957, Serial No. 658,549

6 Claims. (Cl. 60-3932) This invention relates to fuel combustionapparatus, more particularly to afterburner fuel combustion apparatusfor jet propulsion engines and has for an object to provide improvedstructure of this type.

Afterburners of current design employed in aviation jet propulsionengines, such as turbo-jet engines wherein fuel is burned in a gasstream moving at high velocities, are generally provided with stationaryflameholders for providing a sheltered area in which the combustionflame is anchored. The flamesheltering or bluif surface area of suchfiameholders is dictated by engine performance requirements andpermissible fluid pressure drop across the flameholders, hence the totalarea of the blufi surfaces is held to a practical minimum value.

It has been found that with a fixed flameholder of the above type, arelatively long aiterburner shell is required to insure that theportions of the fuel-enriched gas stream flowing in courses notimmediately adjacent the flameholders blufl surfaces are inflamed. Topermit shortening the afterburner shell, it has been proposed tosubstitute a rotary flameholder for the stationary flameholder. Toeifectively. shorten the .afterburner shell in this manner, it has beennecessary to rotate the rotary flameholder at very high speeds, therebyincreasing the velocity of the gas stream relative to the flameholderand rendering the afterburner unstable, i.e., more susceptible toflame-blowout (a well known phenomenon).

In view of the above, it is an object of the invention to provideafterburner fuel combustion apparatus for a jet propulsion engine inwhich the afterburner shell may be shortened considerably whilemaintaining optimum fuel combustion characteristics and reasonablepressure loss without sacrifice in flame stability.

. It is a further object of the invention to provide an afterbumerhaving means for rapidly spreading the flame of combustion across thecombustion chamber with substantially no increase in gas pressure drop.

Another object is to provide, in an afterburner, ainovable structurehaving blades extending across the wake of stationary flameholdingstructure for transporting unburned gases into the wake of theflameholding structure and for transporting burning gases from the wakeinto the unburned gases, thereby to mix the burning and unburned gasesto effect substantially complete combustion of the gases in a shorterlength of time and to permit substantial reduction in length of theafterburner.

Astill further object is to provide, in an afterburner, a structurehaving blades movable into and out of the wakes of the flameholdingstructure and acting as heat exchangers for alternately absorbing heatfrom the burning gases and transferring said heat to the unburned gasesfor combustion purposes.

The invention may assume various embodiments. However, generally'itcontemplates provision of a bladed flame-spreading structure which isrotatably or otherwise movably mounted in spaced relation with anddownstream of suitable stationary flameholding structure. The bladedflame spreading structure may be arranged 2,914,92l Patented Dec. 1, 1959,

. '2 v to autogyrate in the high velocity gas streamlor, if desired, itmay be driven by, a motor orthe like, at a' relativelylow speedg In onerepresentative arrangement, wherein the flame spreading structure isrotatably mounted, the blades are skewed to-a suitable degree to promotemixing or the burning gases anchored to the flameholder structure withthe unburned gases flowing past theflameholder structu're. Thus, theunburned gases are ignited in a considerably shortened length of travelthrough the afterburner and permit, the afterburner .shell to beshortened considerably with no loss in efliciency and no decrease insta-. bility. e f t In another representative arrangement, wherein thebladed structure is rotatably mounted, the blades are unskewed whendriven by a motor, or slightly skewed sufficiently topermitiautogyration in'the gas stream, .With this'arrangement little, ifany, mixing of ,theburning gasesljwitli the [unburned gases is attained.However,

as the blades sweep 'past the burning gases they become highly heatedand as theyv subsequently sweep past the unburned (and cooler) gasesthey transfer heat by direct heat exchange thereto',,,thus heating theunburned gases sufliciently to initiatecombustion thereof. The"foregoing andother objects are effected by the invention as will beapparent from the following description and claims taken in connectionwith the accompanying' drawings, forming apart; of this applicatiom'inwhich: j ,7 'Fig. '1 is an axial sectional'view illustrating the aft endportion of a' typical turbojet propulsion. engine quipped, withanafterburner structure embodying one form of the, invention; T Fig. 2 isa cross-sectional view taken on line l1"II-of f Fig. ,3'i sia viewsimilar'to Fig.1 but'showing another embodiment ofth'e invention; A j

Fig. 4 is a cross-sectional view takenon line IV'-I V ofFig.3;j 7 4 iFig. 5 'is an axial view of a third embodiment of the invention;

Fig.6 isa cross-sectional view taken on li'ne'VI-VI 0f,Fig.5; 1 a

Fig. 7 is an axial view-of a fourthembodiment of the invention; W q

Fig. 8. is. a. cross-sectional view. taken on line VHI VIII of Fig.7; QI. t

Fig. 9 is an axial ,view of afifth embodiment of the invention; .f r YFig. 10 ,is a cross-sectional view taken on line XX of Fig. 9; and q IFig. 11 is a fragmentary view illustrating a portion ,of the structureshown in Fig. 10 on a larger scale. -Referring to'Figs. 1 and 2, thereis shown anatterburner, generally, indicated. '10, mounted to a turbojetengine 11. Only the aft end of the engine 11 has-been illustrated sinceit may be of conventional design and does not form apart of. theinvention. However, as Well known in the art, the engine 11 is providedwith an outer. shell 12 Within which is disposed a turbine 13 and a fuelcombustion chamber 14, wherein fuel is burned in the presence ofpressurized air and the hot combustion gases and unburned air aredelivered to the turbine 13 for motivating the same and then directed.rearwardly through, an annularpassageway 15 defined by a centrallyaligned conical fairingmember 16 and the shell ,12.

The afterburner- 10 is provided with an outer tubular shell or wallstructure 17 open at both ends and bolted to the outer shell 12 of theengine at one end andprovided witha circular exhaust, nozzle 18 at itsother end. A secondary shell or liner 19 of tubular shape may, ifdesired, be concentrically mounted within the outer afterburrier wallstructure 17 for reasons well known in the art. The'liner 19' form'sanaxially elongated combustion chamber 20 through which the gases from theengine 11 are directed to the exhaust nozzle 18 during operation of meda p .L r

An 'ariiiular m'al'iifold structure" 21"whi'ch, as illustrated, may .beformed in three concentric anuul'ar'portions', is providedforinje'ctingfuel into the afterb'urrier combustion chamber and, as wellknowninuie art each of the manifo ld portions' is provided with a"series of fuel injecting nozzles 22. Fuel is delivered to the fuelmanifol'jd'structure' 21 by means of a conduit 23 connected to a fuelsource (not shown). The fuel nozzles 22 are preferably arranged inannular rows to form a symmetrical spray pattern, thereby insuring distmaximum atomization and mixture is effected with the stream of hotcombustion products and air flowing through the passageway 15: 'lh'efuel injecting nia irifd'ld'sma suitably mounted te the afterbur'n'erwar structure 17.1

I Flameholding'structure 2"4is provided in a region downstream or aft ofthe fuel injecting manifoldstructur'e' 21; The fiameholding structure24,as illustrated in this embodiment, is formed of two elongated members25' of V-s'haped cross-section mounted transverselyo'f the liner 19, sothat the bluflf surfaces 26-provide a sheltered region or w'ake in thehigh velocity stream of fuel andair ture" flowing therepast, as wellknown in, theart. The members 25 are disposed in a median positionwithin the passageway 15 and are stationarily mounted to the outer wall17 in any suitable manner.

: Downstream of theflam'eholde'r structure 24 there is provided a freewheeling rotor 28 rotatably mounted in a central position by means of ashaft 29 received in the fairing member 16. The rotor '28 has aplurality of radially disposed blades or vanes 30 which are ofsufficient length to sweep across the entire passageway 15. The bladesare slightly skewed to effect autorotationof' the rotor.

, Variable area nozzle structure 31 maybe provid'e'dfor regulating thearea of the exhaust nozzle 18 as" well known in the art. Inthe'exam'pl'e' shown, the variable area structure 31'has beenillustrated'as' being of the type having a plurality of hinged eye-lidmembers 32" and actuated'by suitable means (not shown).

During operation of the afterburner 10, fuel is delivered by'thecendnit23 to the manifold structure 21' fr'om whence it is injected by the fuelinjecting nozzles 22 into the passageway 15 and mixed with the air andgases flowing therethrough at a high velocity.' The fuel and air mixturethus provided is ignited by suitable means (not shown) to augment thevolume of gases ejected through the nozzle 18' thereby to augment thepropulsive thrust imparted to the engine. However, due to the highvelocityof the stream, the flame is swept downstream and anchored to thebluff surfaces 26 of the flameholder members 25, from'whence it ispropagated to the regions radially inwardly and radially outwardly ofthe flameholder mem'bers. However, heretofore such relatively slowspreading of the flame has made it necessary to provide a relativelylong afterburner combustion chamber.

With the invention, however, the rotor 28 is propelled by the gas flowand assumes a'somewhat stable speed of about 600 r.p.m. due to the skewon the blades 30. During such rotation, the blades 30 sweep through thenon-burning areas of the stream and thence into the flameholding wakearea of the stream, effectin'g mixture thereof andaccelerating thespreading effect of the flame. Also; during such rotation-of the rotor28, some turbulenceis piovided toincrease the mixing action or spreadingaction: Due to the cyclical sweeping of the blades 30 frorri theilameholding wakes (which are relatively lfotfit'othen'onburningportions of the stream (which are relatively cool), the bladetemperatures are alternatel'y heated and cooled. Hence they areprevented from being excessively overheated by the flame and 4. shouldprovide reasonably long and trouble-free service.

In Figs. 3 and 4, there is shown a second embodiment in which anafterburner structure 100 is mounted to the engine 11. Since theafterburner structure 100 may be similar to the afterburner structureshown in the first embodiment, only those members which are modifiedwill be described, it being understood that the other members may beidentical to those illustrated in the first embodiment.

In this embodiment, fuel injecting structure 121 is provided forinjecting fuel into the annular passageway 115. Aft of the fuelinjecting structure 121, there is provided stationary fiameholdingstructure 124, which, as best shown in Fig. 4, is provided with aplurality of members 125 extending radially from an axially alignedfairing member 116 and stationarily supported by the outer wallstructure 117. The flame-holder members 125 are also of V-shaped sectionand serve to form a plurality of radially elongated flame-holding wakesfor anchoring the flame in the'combustion' chamber120. Aft of theflameholder structure 124, there is provided a flame spreading rotor 128which" is provided with an annular row of blades 130 extendingtransversely of and substantially completely across the combustionchamher 120. In this embodiment, the blades are preferably not skewed.However, the rotor 128 is rotatably mounted to the fairing member 116 ina central position by a shaft 129" connected to a driving motor 129a ofany suitable type. As illustrated, the motor 129a is of the air actuatedtype energized by means of air delivered thereto through a conduit 12%connected to a suitable source of pressurized air (not shown).

The embodiment shown in Figs. 3 and 4 operates in a manner similar tothat shown inFigs. 1. and 2. However, in this embodiment, the rotor 128is energized by the motor 129a at a speed of about 600 r.p.m. Since theblades 130 sweep'through the gas stream transversely to the direction offlow thereof, they induce a mixing effect therein and since theyalternately sweep across the unburned portions of the stream and theflameholding wakes, a rapid flame spreading action is provided.

In Figs. 5 and 6, there is shown a third embodiment wherein anafterburner structure 200, having an outer wall structure 217 and innerliner structure 21-9 defining a combustion chamber 220, is provided withfuel in jeeting structure 221 for injecting'fuel into the passageway 215in a manner similar to that described in conjunction" with the first andsecond embodiments. Aft of the fuel injecting structure, there isprovided flameholding structure 224 having elongated bars 225 ofV-shaped section stationa-rily held in the outer wall 217. It will benoted that; in this embodiment, the fiarneholding structure is somewhatsimilar to that shown inthe first embodiment and that a rotor 228 ismounted for rotation about a central axis by meansof a shaft 229received in the fairing member 216. The rotor 228 is provided with anannular series of blades 230 skewed slightly to effect auto-rotation ofthe rotor. However, in this embodimentthe blades 230 are foraminated orotherwise provided with a large number of apertures 226.

The operation of this arrangement is similar to' that of the firstembodiment. However, due to the provision of the apertures 226, a moreactive mixing effect is provided in the a'irstream.

In Figs.- 7 and 8, there is shown'a fourth embodiment wherein acentrally aligned fairing: member 3160f frustoconical shape" isprovided'wi-th a concave rearwardly facing bluff surface portion 324effective as a fiameholder. The flameholding surface 324 provides asingle'but relatively large flame anchoring wake along the central axisof the combustion chamber 320. In this embodiment, the fairing member316 is rigidly received within the afterburner wall structure 317 bymeans of a plurality of struts 326 disposed at the aft end of thefairing member. Al-

though any number of st'rut's may be provided, four have been shown, asseen in Fig. 8. To each of the struts 326, there is attached a rotor 328having a plurality of blades 330 skewed slightly to effect auto-rotationof the rotor. The blades 330 rotate in a plane transverse to the axis ofthe combustion chamber 320 and are of sufiicient radial length toalternately sweep through the flameholding wake and the non-burning fueland air stream, so that, in operation, a thorough mixing action iseffected. u t r p In Figs. 9 through 11, there is shown a fifthembodiment of the invention. In this embodiment, there is provided anafterburner structure 400 having an outer tubular wall structure 417 anda tubularliner 419. An annular series of elongated rods 430 are slidablyreceived at their outer ends in the liner member 419 and at their innerends in a centrally located tubular guide member.

440. The guide member 440 is centrally supported upon a shaft 429received in a fairing member 416. The shaft 429 further has mountedthereon a rotor 428 having an annular row of relatively short vanes 441which are skewed to effect auto-rotation of the shaft 429. Within thehousing 440, there is provided an elliptical cam member 442 which isrigidly attached to the shaft 429 for joint rotation therewith and therods 430 are biased into abutment with the cam member 442 by compressionsprings 443. Also, in a manner similar to that shown in the otherembodiments, there are provided a fuel injecting manifold structure 421for admitting fuel into the combustion chamber 420 and stationaryflameholder structure 424. The flameholder structure may be of anysuitable shape. However, as shown, it is of annular shape and ofV-shaped cross section and disposed upstream of the elongated rods 430.

During operation, the rotor 428 is rotated by air flow past the vanes441, thereby rotating the elliptical cam member 442. As the cam member442 rotates within the guide member 440, the elongated rods 430 are andally translated sequentially in a radial direction against the bias ofthe springs 443 with a reciprocating action. Since the elongated rodsare of such a length as to span the combustion chamber 420, theyalternately receive heat from the combustion flame in the flameholdingwake of the flameholder structure 424 and transfer the heat absorbedthereby into the uninflamed regions laterally of the flameholding wakeby heat exchange action. This action is due to the relatively hot natureof the flameholding wake which is sufliciently high to heat the rods 430to fuel ignition temperatures.

Although in the embodiments outlined above, only the last embodiment hasbeen defined as being effective to transfer heat from the flameholdingwakes to the outer regions of the gas stream, it will now be obviousthat in the first four embodiments, a similar action is attained sincethe blades of the rotor structure are continuously sweeping across thehot inflamed gases in the flameholding wakes and the cool uninflamedgases of the gas stream, thereby alternately absorbing heat from theinflamed portions of the gas stream and transferring their absorbed heatto the uninflamed portions of the gas stream.

It will now be seen that the invention provides a simple arrangement foraccelerating the propagation of flame in an afterburner withoutexcessive fluid pressure drop and without loss of stability.

It will further be seen that the invention provides a relatively simplearrangement for shortening the length of the afterburner shell bypromoting a thorough mixing action and imparting a reasonable amount ofturbulence within the airstream flowing therethrough.

It will also be seen that the invention provides an afterburner whereinflame is spread by means of a heat transfer action as well as by meansof a fluid mixing action.

While the invention has been shown in several forms, it will be obviousto those skilled in the art that it is 6 not so limited, but issusceptible of various other changes and modifications without departingfrom the spirit thereof. a f

What is claimed is:

1. In 'a gas motivated power-plant, wall structure forming a combustionchamber adapted to receive a high velocity stream of air under pressure,means for injectingfuel into said combustion chamber, stationaryfiameholding structure disposed downstream of said fuel injecting meansrelative to direction of flow of ,said air stream, and flame spreaderstructure including a plurality of blades and means for supporting saidblades for movement in a direction transverse to the direction of flowof said air stream, said flame spreader structure being disposeddownstream of said, stationary flameholding structure and said bladeshaving portions movable into and out of the wake of said stationaryflameholding structure.

2. In a jet propulsion engine, tubular wall structure open at both endsand forming an axial-flow combustion chamber adapted to receive a highvelocity stream of air under pressure, means for injecting fuel intosaid combustion chamber, stationary flame-holding structure disposeddownstream of said fuel injecting means relative to direction of flow ofsaid air stream and forming a wake, flame spreader structure including arotor having a plurality of radially disposed blades of elongated shape,and means for rotatably supporting said rotor for rotation about an axissubstantially parallel to the direction of flow of the air stream, saidrotor being disposed downstream of said stationary flame-holdingstructure and presenting a bluff surface of elongated surface areaforming a wake in said air stream similar to the wake of saidflame-holding structure, and said blades being of suflicient radiallength to sweep into and out of the wake of said stationaryflame-holding structure.

3. In a jet propulsion engine, tubular wall structure open at both endsand forming an axial flow combustion chamber adapted to receive a highvelocity stream of air under pressure, means for injecting fuel in asymmetrical pattern into said combustion chamber, stationaryflameholding structure disposed downstream of said fuel injecting meansrelative to direction of flow of said airstream, and flame-spreaderstructure including a rotor disposed downstream of said stationaryflame-holding structure, said rotor having an annular row of radiallyextending blades, said blades being skewed relative to the axis of saidcombustion chamber, and means including a shaft for rotatably supportingsaid rotor in a central position within said combustion chamber, saidstationary flame-holding structure having a plurality of transversebluff surface portions adapted to form a plurality of flame shelteringwakes extending past the path of travel of said blades.

4. In a turbojet engine including an afterburner, an

' outer tubular wall enclosing a combustion chamber, an

inner axially-extending fairing member carried therein and forming anannular passageway through which a high velocity stream of air isadmitted to said combustion chamber, means for injecting fuel into saidpassageway in a symmetrical pattern, a stationary flame-holder disposeddownstream of said fuel injecting means, said flameholder being providedwith a plurality of radially extending arms having transversely disposedbluff surface portions adapted to form a plurality of flame-holdingWakes, means for spreading the flame from said wakes to uninflamedportions of said high velocity stream including a centrally disposedrotor having a plurality of radially extending blades, and meansincluding a shaft disposed in said fairing member for rotatablysupporting said rotor.

5. In a turbojet engine including an afterburner, an outer tubularwallenclosing a combustion chamber, an inner axially extending fairingmember carried therein and forming an annular passageway through which ahigh velocity stream ofv exhaust gases and air from the engine isadmitted to said combustion chamber, means for inj ecting fuel into saidpassageway, said fairing member being of substantially frusto-conicalshape and having a downstream facingend portion disposed downstream ofsaid fuel injecting means and substantially normal to the axis of saidshell, said end portion thereby being adapted to form a-centrallydisposed flame-sheltering make and means forspreading the flame fromsaid wake to uninfiamed portions of said stream including a plurality ofrotors disposed in said combustion chamber downstream of said endportion, means for rotatably supporting said rotors, each of said rotorshaving aplurality of radially extending blades of suflicientlength tosweep past a part of said wake during one portion of their travel andpast a partof said uninflamed portion d'uri'ng another portion of theirtravel.

6. Ina turbojet engine including an afterburner, atubular wall open atopposite ends and defining an axial flow combustion chamber adapted toreceive a high velocity stream of air unden pressure, means forinjecting fuel into said combustion chamber, stationary flameholdingstructuredisposed-downstream of said fuel injecting, means relative tothe direction of flow of said airstream; and flame-spreader structuredisposed downstream of saidstationary flame-holding structure includinga plurality of elongated members disposed transversely to thcaxis ofsaid'wall and extending through the wake of said flame-holding structureinto the uninfiarned regions of said combustion chamber, means forsupporting said elongated members for straight line movement transverseto the axis of said wall, and means for periodically moving the same.

No references cited.

